A propulsion engine, such as a jet engine, may be mounted at various points on the aircraft by being attached to a strut or a pylon belonging to the aircraft structure. It may thus be suspended under the wing, fastened to the fuselage, generally at the rear, or mounted in the tail unit using suitable attachment means. The function of these attachment means is to ensure that mechanical forces are transmitted between the engine and the structure of the aircraft. The loads to be taken into consideration are oriented in the three main directions of a reference frame linked with the engine. These are in particular the weight of the engine along the vertical axis Z, its thrust along the axis X of the engine, and the lateral aerodynamic loads along the transverse axis Y. The loads to be transmitted also comprise the torque taken up around the axis of the engine. These means must additionally absorb the deformations experienced by the engine during the various flight phases, resulting, for example, from dimensional variations due to thermal expansions or contractions, without transmitting these deformations to the strut.
The connection between the engine and the strut is generally provided in the case of fan engines by means of two suspension planes, one at the front of the engine at the level of the intermediate casing, the other at the rear. Each of the suspension means is designed to transmit some of the forces. For example, one of the suspensions is responsible for taking up or transferring lateral forces along the axis Y and vertical forces along the axis Z, and also for taking up the engine torque around the axis X. The other suspension is responsible for transmitting the thrust and also the lateral and vertical forces to the aircraft strut. Such a suspension is isostatic.
Generally, a suspension means comprises a beam, if appropriate a double beam, fastened to the strut by means of bolts and connected to the engine casing by means of links. Depending on their mounting, the links pivot at their ends on devises or tabs which are secured to the engine casing and to the beam, respectively. To ensure that the transmission of the forces by the links is purely axial, that is to say along the axis of the links, there is provided a swivel-type bearing for the pins passing through, at each end of the links. This type of mounting makes it possible. in particular to absorb the radial and axial expansions of the engine.
Safety-related constraints also demand the presence of means which overcome the failure of a force-transmitting element. To this end, these suspensions are thus generally provided with connecting means having a clearance, known as standby means, which become active by absorbing the clearance and transmit the forces via a safety path if one of the transmissions becomes defective following the breaking of a piece.
U.S. Pat. No. 5,860,623 discloses a rear suspension for suspending a jet engine on an aircraft strut, comprising a beam running transversely with respect to the axis of the engine and connected by three links to the engine casing. The beam comprises a platform having means for fastening it to the strut by bolting. It is distinguished by first and second lateral links each connected by a first pin to the beam and by a second pin to a fitting secured to the engine casing. These links are arranged on either side of the axis of the engine. A central link is arranged between the two lateral links and is likewise connected by a first pin to the beam and by a second pin to the fitting. In normal operation, the function of these three links is to transmit the vertically and laterally oriented forces and also the engine torque to the strut.
One of the two lateral links comprises a finger which prolongs it in the region of the first pin. This finger is housed with clearance in an orifice provided in a rib of the beam. This rib is perpendicular to the plane of rotation of the link and the clearance is sufficient for the movements of the link not to be blocked in normal operation. The mounting is isostatic. Should a breakage occur in a connection of the first link or of the central link, the clearance is eliminated by the engine tilting around the axes of the other two links, and the connection remains isostatic. The other links assume the transfer of all the forces on this suspension.
There is a second connection, a standby safety connection, between the central link and the engine casing in the form of a connecting pin which passes both through the central link and through a clevis secured to the engine casing. This pin is mounted with a clearance on either the link or the clevis. This clearance is eliminated in the same way as above when one of the other connections becomes broken, and the forces are then transferred via the remaining connections.
The objective set by the Applicant is to produce a suspension which performs the same functions as those featured in the above patent but which is simpler to manufacture while at the same time satisfying the strength and reliability constraints.